Whether it was an epic publicity stunt or a genuine mishap remains a topic of debate in some circles. Either way, the cover shoot for 1977's Animals became one of Pink Floyd's signature moments.

Roger Waters and artist Aubrey Powell, co-founder of the art group Hipgnosis, came up with the concept of an inflatable pig floating over Britain's iconic Battersea Power Station. But things didn't go as planned at the Dec. 3, 1976 photo shoot, as the 40-foot balloon broke from its moorings on one of Battersea's southern chimneys, rising directly into the path of planes landing at Heathrow Airport. All flights were grounded, and Powell was arrested, even as police helicopters and the Royal Air Force arrived to chase the pig. It eventually fell to the ground miles way in Kent.

"At 9:30PM, a man rang up," Powell recalled in an interview with Time Out London. "He said, 'Are you the guy looking for a pig? It’s scaring my cows to death in my field.' It was front-page news. Pink Floyd couldn’t have got better publicity if they tried."

But they still didn't have a cover image. Powell and the band returned to Battersea later, this time with a sharpshooter in tow to take out any errant balloons, but the lighting had changed. (Powell still marvels over "the most incredible, [Joseph Mallord William] Turner-esque sky" they had for the first shoot.) He ended up cutting and pasting an image of the pig onto one of his earlier pictures of the power station. "It’s actually a completely faked photograph," Powell later confirmed.

Animals would reach the Top 10 in both the U.S. and the U.K., selling more than four million copies. The pig, which Waters had named Algie, became a concert staple. Meanwhile, Battersea Power Station officials report that a large percentage of visitors to the now-closed facility are still Pink Floyd fans.

"I'd always loved Battersea Power Station, just as a piece of architecture," Waters subsequently told Rolling Stone. "And I thought it had some good symbolic connections with Pink Floyd as it was at that point. One, I thought it was a power station, that’s pretty obvious. And two, that it had four legs. If you inverted it, it was like a table. And there were four bits to it, representing the four members of the band."

In 2011, a replica of the original pig floated again between the two iconic chimneys, in celebration of a massive reissue project from the band.

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